For the outside air intake on the side we use either a flexible aluminum line or a rigid elbow right off the unit. We screw it to the collar and then use FOIL tape to make it secure. Once away from the unit we switch to an insulated 6" duct and run that to the outside of the house. For the chimney air kit (which is required) we use a 4" flexible hose to get away from the unit and then again switch to an insulated duct. We use foil tape on all joints for heat resistance. We also caulk the chimney air kit to the unit and pipe on top with high temp red silicone. The pipe does not have to be exactly centered in the firestop. There is new UL testing that allows us to caulk to gaps in the firestops for the SL300 pipe as it penetrates into the attic. This prevents cold air from flowing down from the attic.